A versatile, highly reactive, cross-linking reagent: 2,2'-sulfonylbis[3-methoxy-(E,E)-2-propenenitrile]

Bis[2-(3-carboxyphenoxy)carbonylethyl]phosphinic acid (m-BCCEP): a novel affinity cross-linking reagent for the beta-cleft modification of human hemoglobin

The design and synthesis of bis[2-(3-carboxyphenoxy)carbonylethyl]phosphinic acid (m-BCCEP, 1) as a site-directed affinity reagent for cross-linking human hemoglobin have been reported as part of our long-term goal to generate artificial blood for emergency transfusions. Molecular modeling techniques were used to design the reagent, employing crystal coordinates of human hemoglobin A(0) imported from the Protein Data Bank. It was synthesized in four steps commencing from 3-hydroxybenzoic acid. The reagent 1 was converted to its trisodium salt to allow effective cross-linking in an aqueous medium. The reagent 1, as its trisodium salt, was found to specifically cross-link stroma-free human hemoglobin A(0) in the beta-cleft under oxygenated reaction conditions at neutral pH. The SDS-PAGE analyses of the modified hemoglobin pointed to the molecular mass range of 32 kDa as anticipated. The HPLC analyses of the product suggested that the cross-link had formed between the beta(1)-beta(2) subunits. Molecular dynamics simulation studies on the reagent-HbA(0) complex suggested that the predominant amino acid residues involved in the cross-linking are N-terminus Val-1 or Lys-82 on one of the beta-subunits and Lys-144 on the other. These predictions were borne out by MALDI-TOF MS analyses data of the peptide fragments obtained from tryptic digestion of the cross-linked product. The data also suggested the presence of a minor cross-link between Val-1 and Lys-82 on the opposing subunits. The oxygen equilibrium measurements of the m-BCCEP-modified hemoglobin product at 37 degrees C showed oxygen affinity (P(50) = 25.8 Torr) comparable to that of the natural whole blood (P(50) = 27.0 Torr) and significantly lower than that of stroma-free hemoglobin (P(50) = 14.19 Torr) assayed under identical conditions. The measured Hill coefficient value of 1.91 of the m-BCCEP-modified Hb product points to the reasonable retainment of oxygen-binding cooperativity after the cross-link formation.

A Novel Site-Directed Affinity Reagent for Cross-Linking Human Hemoglobin: Bis[2-(4-phosphonooxyphenoxy)carbonylethyl]phosphinic Acid

Bis[2-(4-phosphonooxyphenoxy)carbonylethyl]phosphinc acid (BPPCEP) was prepared and evaluated as a site-directed affinity reagent for cross-linking human hemoglobin. It was synthesized in four steps starting from 4-benzyloxyphenol and was converted to its pentasodium salt so as to afford efficient cross-linking in an aqueous medium. The reagent was found to specifically cross-link human hemoglobin A(0) in the beta-cleft chains under oxygenated reaction conditions at neutral pH. The amino acid residues involved in the cross-linking were determined by mass spectral analyses of tryptic digest fragments of cross-linked hemoglobin, employing a MALDI-TOF mass spectrometer. The MS analyses suggested that the most likely amino acids involved in the cross-links are Val-1 or Lys-82 present on one of the beta subunits and Lys-82 or Lys-144 on the other. Molecular modeling studies performed on the reagent-HbA(0) complex corroborated the conclusions reached by MALDI-MS analyses. The oxygen equilibrium measurements of the three major BPPCEP-cross-linked Hb products, isolated and purified by preparative cation exchange chromatography, exhibited oxygen affinity (P(50)) values of 14.5, 12.1, and 15.5 Torr as compared with the P(50) of 13.1 Torr for cell-free hemoglobin. The oxygen-binding cooperativity of the modified products, as determined by the Hill coefficient generated from the Hill plots of the respective P(50) values, coupled with the absence of sigmoidal shape of the O(2) equilibrium curves, was considerably lower than that of the native hemoglobin.

Affinity reagents for cross-linking hemoglobin: bis(phenoxycarbonylethyl)phosphinic acid (BPCEP) and bis(3-nitrophenoxycarbonylethyl)phosphinic acid (BNCEP)

Synthesis and properties of two new macrobiomolecular cross-linking reagents, bis(phenoxycarbonylethyl) phosphinic acid (BPCEP) and bis(3-nitrophenoxycarbonylethyl)phosphinic acid (BNCEP), have been reported. The reagents were successfully employed to cross-link human hemoglobin under oxygenated conditions. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), high performance liquid chromatography (HPLC), and fast protein liquid chromatography (FPLC) analyses of the reaction products indicated that the cross-link was intramolecular in nature, and that it was between the two beta subunits of hemoglobin in each case. The products were purified by DEAE-cellulose chromatography, and the purified material was employed for oxygen-binding assessments. The oxygen equilibrium curve of the cross-linked material, in each case, was right-shifted toward lower oxygen affinity as desired. The sigmoidal shapes of oxygen curves, in each case, suggested retainment of oxygen-binding cooperativity, although considerably lower than that of the native hemoglobin

Bis[2-(4-carboxyphenoxy)carbonylethyl]phosphinic acid (BCCEP): a novel affinity reagent for the beta-cleft modification of human hemoglobin

The design, synthesis, and hemoglobin cross-linking studies of a novel organic reagent, bis[2-(4-carboxyphenoxy)carbonylethyl]phosphinic acid (BCCEP, 1) have been reported. The reagent was designed with the aid of molecular modeling, employing crystal coordinates of human hemoglobin A0. It was synthesized in three steps commencing from 4-t-butoxycarbonylphenol. The tri-sodium salt of 1 was employed to cross-link human oxyHb. While SDS-PAGE analyses of the modified hemoglobin product pointed to the molecular mass range of 32 kDa, the HPLC analyse suggested that the cross-link had formed between the beta 1-beta 2 subunits. The oxygen equilibrium measurements of the modified hemoglobin at 37 degrees C showed significantly reduced oxygen affinity (P50 = 31.3 Torr) as compared with that of cell-free hemoglobin (P50 = 6.6 Torr). The sigmoidal shape of O2 curves of the modified Hb pointed to reasonable retainment of oxygen-binding cooperativity after the cross-link formation. Molecular dynamics simulation studies on the reagent-HbA0 complex suggested that the most likely amino acid residues involved in the cross-linking are N-terminus Val-1 or Lys-82 on one of the-chains, and Lys-144 on the other. These predictions were consistent with the results of MALDI-MS analyses of the peptide fragments obtained from tryptic digestion of the cross-linked product.

Reagents for bioorganic synthesis. 6. The design and synthesis of two novel polyfunctional organic reagents for biomacromolecular modification

The design, synthesis, structure, and properties of two tetrafunctional organic reagents, namely, 2,2'-sulfonylbis[3-(carboxymethylamino)-(E,E)-N-(2-chloroeth yl)propenamide] (SBCCP) (1) and 2,2'-sulfonylbis[3-(carboxymethylamino)-(E,E)-N-(2-oxoeth yl)propenamide] (SBCOP) (2) are reported. Reagents 1 and 2 contain reactive bis(alkyl halide) and bis(aldehyde) functions, respectively, as well as bis(carboxylic acid) moieties. The reagents have potential applications for biomacromolecular cross-linking, in particular for the cross-linking of hemoglobin subunits. Single-crystal X-ray diffraction data of synthetic intermediates (4,5, and 12) provided information about structural features and tether lengths of the target reagents.